The invention generally relates to a bipolar medical instrument having two jaw parts disposed at the distal end of a tubular shaft, where the two jaw parts are pivotally joined to one another and wherein each jaw part forms an electrode to which high frequency electrical power can be applied.
The German patent DE 196 08 716 discloses such a bipolar medical instrument. The instrument is employed in minimally invasive surgery on the human or animal body in endoscopic operations.
The two jaw parts at the distal end of the tubular shaft are pivotally joined, so that the two jaw parts are opened and closed through actuation of handling means at the proximal end of the tubular shaft. Body tissue is cut and/or grasped with the jaw parts to separate and remove tissue or to shift or move tissue. The jaw parts are correspondingly formed as cutting tools with cutting edges or as grasping tools where the jaw parts when closed engage one another with blunt surfaces.
At least one of the two jaw parts is pivotally joined to the tubular shaft, while the other jaw part is either pivotally or rigidly secured to the shaft.
It is also foreseen in the instrument mentioned at the outset, that both jaw parts form electrodes, to which high frequency electrical power can be supplied. The two jaw parts are each connected respectively with one pole of a high frequency voltage source. When applying bipolar high frequency power, the two jaw parts when acting as a cutting tool achieve a better cutting effect due to the thermal effects of the high frequency current. On the other hand, when acting as a grasping tool a coagulation of the tissue grasped between the jaw parts is achieved through heat generation.
Since the jaw parts, the pivot joint of the jaw parts and the tubular shaft are normally made of metal and are therefore electrically conductive, the problem arises that electrical insulation between the jaw parts forming electrodes must be provided to avoid a short circuiting of the jaw parts, because different potentials are supplied to the jaw parts. The problem of electrical isolation of the two jaw parts is even greater, the smaller the size of the instrument in the jaw part region and in the region of the pivot. This is especially the case when the diameter of the instrument in the pivot region is 5 mm or less.
In the instrument disclosed in DE 196 08 716, electrical insulation is achieved in that ceramic elements are placed in the pivot joint of the two jaw parts, which is otherwise made of metal. The ceramic elements then also form a part of the pivot joint. This type of insulation of the two jaw parts in the pivot region however has the drawback that the ceramic elements must be strongly reduced in thickness if the instrument is to be miniaturized. The normal high frequency voltage on the jaw parts is in the order of 2.5 kV, which means that when reducing the thickness of the ceramic elements, a voltage spark through the ceramic element can take place. A further drawback of the electrical insulation in the pivot region is that the ceramic elements move with the jaw parts and thus are subject to abrasion due to friction over time.
Another bipolar medical instrument is disclosed in the German patent application DE 43 12 284, wherein the jaw parts are completely made of plastic in which the ends of the electrical lines are embedded. The drawback here is that the jaw parts supplied with high frequency power may not always withstand the high heat generation.
The object of the present invention, therefore, is to provide an improved bipolar medical instrument of the type mentioned at the outset, wherein a reliable electrical insulation with constructively simple means is achieved, especially in a miniaturized configuration of the jaw parts and the pivot joint of the two jaw parts.
According to the present invention, a bipolar medical instrument is provided, comprising:
a tubular shaft having a distal end;
a first and a second jaw part disposed at said distal end of said shaft, said first and second jaw part being pivotally joined to one another, said first jaw part forming a first electrode and said second jaw part forming a second electrode, to which high frequency electric power can be applied;
a first and a second insulated electrical line extending through said tubular shaft, said first electrical line being conductively connected to said first electrode and said second electrical line being conductively connected to said second electrode, each of said first and second jaw part comprising:
a metallic base, said metallic base of said first jaw part being pivotally joined to said metallic base of said second jaw part;
an insulator element disposed on a side of said metallic base facing the other of said first and second jaw part, respectively; and
a conducting element joined to said insulator element, which forms said first and second electrode, respectively, and is not in contact with said metallic base and is conductively connected to one of said first and second electric line, respectively.
Instead of insulating the two jaw parts at the pivot joint as in the prior art, the instrument according to the present invention provides electrical insulation on the jaw parts themselves. However, the jaw parts are not formed completely of an insulating material, for example plastic as in the prior art, but each comprises a metallic base giving the necessary high mechanical stability of the jaw parts, which is advantageous for such instruments. The electrical insulation is accomplished by the insulator elements arranged on the sides of the bases facing one another, so that an electrical isolation is achieved. A conductive element is connected respectively to each insulator element to form the electrodes to which high frequency power can be applied. Electric power supply is provided by insulated electrical lines running through the tubular shaft, which extend to and are connected to the conductive elements. The conductive elements are separated from the metallic bases by the insulator elements, so that the jaw parts which are pivotally journaled at the bases are insulated from one another.
In contrast to the prior art, the pivotal connection of the two jaw parts can be metallic and electrically conductive, where isolation measures in the pivot region requiring more space are avoided. The instrument of the present invention can therefore be greatly reduced in size without loss of stability at the pivot joint, because insulation materials, which do not have the same mechanical stability as metals, are avoided as components of the pivot joint.
In a preferred embodiment, a distal end of each of said first and second electrical line is arranged in and enclosed by said associated insulator element and is electrically connected to a projection of said conductive element projecting into said insulator element.
The advantage is that each electrical line is reliably, mechanically secured within its insulator element and on the other hand the conductive element is mechanically secured to the insulator element by the projection extending into the insulator element.
Preferably, said distal end of each of said first and second electrical line is passed through said insulator element from a proximal end thereof to a distal end thereof and is inserted to a small tube of said conductive element which projects into a distal end of said insulator element.
The complete embedding of the electrical line in the insulator element has the advantage that the electrical line is better secured within the insulator element. The electrical lines can be formed of a thin wire surrounded by an insulating mantle. A further advantage is that the electrical line with its insulating mantle can be inserted into the proximal end of the insulator element, so that a possible contact of the electrical line with the metallic base of the respective jaw part is reliably avoided. The outmost distal end of each electrical line, which is then not insulated, is inserted into the tube of the conductive element projecting into the insulator element. In this manner, a reliable electrical contact of the electrical line with the conductive element is achieved.
In a further preferred embodiment, said insulator element distally extends beyond said metallic base and said conductive element is arranged at least on a distal end of said insulator element and forms a tip.
In this embodiment, the effective electrode surfaces of the two jaw parts are located at their respective distal ends, so that tissue can be treated with high frequency power with the tip. With the insulator element extending beyond the associated metallic base to the distal end, a reliable separation of the conductive elements, i.e. the electrodes and the metallic base is achieved.
In a further preferred embodiment, said tip terminates in a branch in a tweezer-like fashion.
This has the advantage that the tweezer-like branches allow a particularly fine treatment of tissue under the influence of the high frequency energy. The peaked branches cause an increased high frequency power density due to a peak effect, so that a cutting function or a cutting-like property of the instrument is possible without having to provide scissor-like cutting means.
Preferably, said conductive element encloses a distal end of said insulator element in the form of a cap.
The advantage is that the conductive elements provide a protective cover of the distal ends of the insulator elements so that the distal ends, which for example are made of ceramic and are less abrasion resistant, are protected against wear.
In a further preferred embodiment, said conductive element has a plate-like form and extends substantially over the entire surface of said insulator element, i.e. the surface of the jaw part opposing the surface of the other of said jaw parts.
With this feature the effective electrode surface of the two jaw parts is advantageously enlarged, so that large surface areas of tissue grasped between the jaw parts can be treated with high frequency electrical energy, i.e. coagulated.
In a further preferred embodiment, said insulator element extends beyond said metallic base in circumferential direction.
With this feature, a sufficiently large spacing of the two metallic bases is achieved in constructively simple manner also along their longitudinal sides in the region of the conductive elements acting as electrodes. A spark discharge is therefore avoided even at high voltages.
In a further preferred embodiment, said insulator element is seated in said respective metallic base.
The advantage is that the insulator elements are securely retained in the metallic bases even at high mechanical loads, which for example can arise when cutting or grasping tissue by closing the jaw part.
In a further preferred embodiment, said insulator element is fixed to said metallic base by means of an adhesive.
A particularly simple and stable connection of the insulator element with the metallic base is achieved, which is also secure against release.
Preferably, said adhesive is heat resistant and/or moisture resistant.
An advantage is that the connection between the insulator element and the metallic base is secure when heat is generated in using the instrument. A further advantage is that the jaw parts can be sterilized in an autoclave at high vapor pressures and high temperatures, so that the present instrument fulfills the strict requirements with respect to sterilization.
In a further preferred embodiment, said insulator element is made of a ceramic material, preferably a ceramic material of high hardness and of less brittleness.
The advantage is that the insulator element of each jaw part possesses high mechanical stability. As the insulator elements are disposed in the working area of the jaw parts and thus make up part of the grasping or cutting tool, a high stability of the jaw parts is achieved, even with high force exertion.
Further advantages can be taken from the following description in connection with the appended drawings. It will be understood that the above-mentioned features and those to be discussed below are not only applicable in the given combinations, but may also be employed in other combinations or taken alone without departing from the scope of the present invention.
An embodiment of the present invention is illustrated in the drawings and will be discussed in more detail below.